The invention relates generally to integrated circuits and more particularly to an integrated resistor having a contact that is aligned with the resistor body and a method for forming the resistor.
As their customers continue to demand new versions of integrated circuits (ICs) that are smaller and more functional than prior versions, IC manufacturers try to include more integrated components such as resistors, transistors, and capacitors per unit area of an IC die. One technique for achieving this result is to minimize the layout area that an integrated component occupies.
FIG. 4(c) of U.S. Pat. No. 5,236,857 entitled RESISTOR STRUCTURE AND PROCESS discloses an integrated resistor 10 having a resistor body 14 and resistor heads 16, which are low-resistance contacts for coupling the body 14 to other integrated components.
One problem with the integrated resistor 10 is that it occupies more than its optimal layout area, and thus may hinder a manufacturer""s efforts to decrease the size of an IC that incorporates the resistor 10. Specifically, the optimal layout area of the resistor 10 is the area occupied by the heads 16 and the body 14 where the edges of the heads and body are aligned. To allow for potential misalignment during the manufacturing process, however, the manufacturer makes the body 14 significantly wider than the heads 16. Unfortunately, this widening of the body 14 increases the area of the resistor 10 beyond its optimal area. In addition, this widening tends to decrease the resistance of the resistor 10. Therefore, so that the resistor 10 has the desired resistance, the IC manufacture proportionally lengthens the body 14. Lengthening the body 14 tends to increase the resistance of the resistor 10, and thus counteracts the resistance decrease caused by the widening of the body 14. Unfortunately, this lengthening of the body 14 further increases the area of body 14, and thus further increases the area of the resistor 10 beyond its optimal area.
An integrated resistor includes a layer of semiconductor material having a first edge. A first region having a first conductivity is disposed in the layer contiguous with the first edge. A second region having a second conductivity is also disposed in the layer contiguous with both the first edge and with the first region, and the second conductivity is different than the first conductivity.
Because such a resistor can include an aligned body and contact, the resistor often occupies a smaller area than a prior integrated resistor having a similar resistance.